1. How is sound made?
  • Sound:It’s caused by the vibrations of objects. Everything that was making a sound was vibrating.
2. How does sound travel through the air?
  • Sound can transmit energy through the air, not the air itself.
  • If it’s air, it’s not sound, it’s Wind.
3. voicewithwaveWhat are the same key characteristics?
  • Energy can be transmitted through the medium, not the medium itself.
  • The medium can be gas, liquid or solid
  • Therefore, we also call soundSound waves
4. Here we can solve a long-standing puzzle for many people: Why does a recorded voice sound different from a spoken one?

  • When I speak, I actually hear two sounds, one from two different media. ① Sound wave → air → ears ② Sound wave → flesh, bone and other media → ears
  • When listening: Sound wave → air → ear
5. And how does the human ear hear sound? (understand)
  • The process is as follows: the source of sound → the auricle (which collects sound waves) → the external auditory canal (which transmits sound waves) → the eardrum (which converts sound waves into vibrations) → the auditory ossicle (which amplifies vibrations) → the cochlea (which converts vibrations into electrical signals) → the auditory nerve (which transmits electrical signals) → the brain (which creates hearing)
6. What is the equilibrium position? What is amplitude?

  • If you look at a single molecule of air, you can see that the way it vibrates back and forth is a graph of a sine or cosine function.
  • The blue center line represents the undisturbed Equilibrium Position of the air molecule.
  • The distance from the equilibrium position to the maximum displacement position is called Amplitude.
7. What is a cycle? What is frequency?

  • The time it takes for an air molecule to vibrate completely once is called a Period, measured in seconds.
  • The number of times an object vibrates back and forth per second is calledFrequency, that is,Cycle fraction.
  • ① The unit is one second (1/s), also known as Hertz (Hz)
  • ② For example, 440Hz means that the object vibrates 440 times per second
  • ③ In this way, the frequency is used to indicate the speed of the vibration of the object
8. What is the theoretical difference between the frequency of human sounds and the frequency of hearing? (understand)
  • In theory, the human voice frequency is between 85Hz and 1100Hz, and humans can only hear sounds between 20Hz and 20000Hz.
  • Below 20Hz is called Infrasound
  • Higher than 20,000 Hz is called: Ultrasound
9. What is pitch?
  • The higher the frequency, the higher the pitch; The lower the frequency, the lower the pitch.
10. What is loudness?
  • When you increase the loudness (volume, volume) of a sound, the amplitude of the vibration becomes larger.
  • We often use dB to describe the loudness of a sound.
11. Why do we recognize different people’s voices? What is timbre?
  • Timbre refers to the character of the sound.
  • ① Different sound sources because of their different materials and structures, the sound timbre is also different
  • ② The reason why we can distinguish different Musical Instruments and different people by their sounds is that they have different timbre
  • ③ Sounds of different timbre can be distinguished even in the same loudness and pitch
12. The principle of different timbre?
  • Usually the vibration of the sound source does not produce a single frequency sound wave, but a composite sound made up of fundamental and overtones of different frequencies.
  • ① When the main body of the sound source vibrates, a Fundamental Frequency will be emitted.
  • ② At the same time, the other parts also have compound sound sources, which combine to produce overtones
  • ③ Overtones are actually the physical harmonics.
  • Pitch is determined by pitch, and timbre is determined by overtones.